1. Field of the invention
The invention in general relates to semiconductor devices and more particularly to a solid state transistor structure which can be used as an amplifier or as a switch for switching high voltages.
2. Description of Related Art
Power switches are used for switching high voltages and high currents on and off, and are utilized in many arrangements for power conditioning systems such as DC/AC inverter circuits. Ideally, this switching of high voltages could be accomplished by a single normally off device that could both block high voltages in the off state and have low resistance in the on state.
One such candidate is the well-known SIT (static induction transistor. Typically, this device is normally on and is switched off by applying a negative bias to its gate. A normally off SIT can be created by positioning the gate regions of the SIT relatively close together. The normally off SIT however can suffer from relatively high on resistance because the tight spacing between the gate regions creates a very thin channel region. The problem significantly worsens as the normally off blocking voltage is increased. In addition, a single normally off SIT device can have a reduced switching speed due to the large gate to drain capacitance.
The present invention solves the problem by providing a device which can block very high voltages in the off state, provide very low resistance in the on state, and switch at high frequency.